It was only a matter of time. LinkedIn CEO Jeff Weiner knew it was coming, industry insiders have speculated about it, I've mentioned it on more than one occasion: Facebook (NASDAQ:FB) was going to start playing in LinkedIn's (NYSE:LNKD) sandbox. Turns out, that time is now.

Facebook announced the launch of its Social Jobs App on Nov 14, in partnership with public agencies, including the U.S. Department of Labor, and online job hunting industry leaders Monster.com (NYSE:MWW), among others. As LinkedIn aficionados are aware, its Talent Solutions unit is the primary revenue generator among its three divisions. In the most recent quarterly earnings announced Nov. 1, LinkedIn's talent solutions was responsible for over $138 million in revenue, more than the Marketing Solutions and Premium Subscriptions units combined.

It's about time
Facebook continues to struggle in its efforts to successfully translate its billion users to revenue; that's no secret. The strides that Facebook's made in the exploding mobile computing market, though pooh-poohed by some, are impressive, and shouldn't be discounted. In its most recent quarter, CEO Mark Zuckerberg sounded (almost) giddy when he referred to the 600 million users that used their mobile devices to access Facebook -- as well he should. Of the $1.1 billion in ad revenue in Q3, about $150 million came from Facebook's mobile efforts, three times the prior quarter's results.

As nice a trend as the mobile computing results are for Facebook, they're also a concern. The 86% of total revenues Facebook earns from advertising clearly demonstrates its lack of diversification. And that's an area that LinkedIn excels in, and always has.

LinkedIn isn't likely to roll over
As a rule, I consider myself a staunch value investor. Strong, consistently performing stocks, flying under the radar, have traditionally offered the most appeal. But every now and again, a LinkedIn crops up.

Unlike Groupon (NASDAQ:GRPN), for example, Weiner and the LinkedIn team have always understood the importance of maximizing its most valuable asset – 187 million users. Groupon has just recently rolled out its Payment Service, to go along with the relatively new Groupon Goods, the iPad-specific Breadcrumb app for merchants, and its bread-and-butter online coupons. LinkedIn? Its three revenue drivers have been a part of its strategy from the get-go, and it shows.

LinkedIn's current valuation is off the charts, with a trailing P/E over 640, and price-to-book and price-to-sales ratios that are head and shoulders above the industry. But there's more to LinkedIn than current measures; a lot more. LinkedIn's talent, marketing and premium solutions divisions grew 95%, 60%, and 74% in Q3, respectively, compared to the year-ago period. With that kind of growth, it's not surprising that LinkedIn's forward P/E is 76. It's still high, but it gives you an indication of its outstanding growth potential.

Turns out that fund manager George Soros is another LinkedIn fan. Soros Fund Management's most recent quarterly SEC filing included adding 1.2 million shares of LinkedIn, valued at about $141 million. Soros still owns Facebook, too, but pared his holdings by 41,000 shares in the past quarter.

The impact
It was only a matter of time before Facebook began expanding its services, and revenue opportunities, to better utilize its 1 billion members. If Zuckerberg didn't do it, former Google executive, and now Facebook COO, Sheryl Sandberg would have – that's why she's there.

Is Facebook's new jobs app a threat to LinkedIn's primary revenue drivers? You bet, and it's the first of many. It won't be long before Google's (NASDAQ:GOOGL) fast-growing Google+ service -- it's already at 400 million members, and growing rapidly -- transitions from a social media hotspot to a direct competitor of LinkedIn. If Google's proven anything during the past several years, it's that when the $212 billion online behemoth decides to enter a market, it goes all in.

But here's the thing -- LinkedIn is extremely well managed, and too firmly established in its key markets to be surprised or irrevocably damaged by the likes of Facebook, Google, or anyone else for that matter. It'll be a challenge, of that you can be certain; but LinkedIn has been preparing for this day since its inception.

Tim Brugger has no positions in the stocks mentioned above. The Motley Fool owns shares of Facebook, Google, and LinkedIn and has the following options: long JAN 2014 $20.00 calls on Facebook. Motley Fool newsletter services recommend Facebook, Google, and LinkedIn. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.